Underground utilities, such as storm sewers and other fluid lines, require a flow line to be bored in the ground beneath the surface. Accuracy in the boring process is essential for proper flow through the line. Various methods have been utilized for boring the flow line and installing the pipes therein. These methods include open digging or trenching, tunneling and auger boring, and directional drilling. Each of these methods of boring the flow line has problems and limitations.
For example, open digging presents hazards for workers in the trench. Also, the large size of the trench created by open digging requires extensive time to dig and refill. Furthermore, the pipe in the trench must be backfilled with gravel or similar material to keep the pipe in place. The equipment used in tunneling is complex and expensive, and typically not cost effective for bores having a diameter of less than two to three feet. The tunnel equipment is also bulky and heavy. The pipes used in the tunnels are also expensive. Auger boring lacks guidance, and therefore presents difficulty in creating the proper grade and line. Also, the pipe in both tunneling and auger boring is installed within the bore by a jacking process, and thus must have sufficient strength to withstand the jacking forces. In both tunneling and auger boring, it is sometimes necessary to provide a carrier pipe within a larger pipe to prevent corrosion and provide proper grade.
The directional drilling process eliminates many of the problems associated with open trenching, tunneling and augering, but also has drawbacks, such as lack of accuracy in the electronic tracking components so as to provide proper line and grade for the flow line. Also, the pipes are subjected to substantial pressure from the slurry in the bored hole, and the pipe can float or deflect if the bored hole is too large.
Therefore, a primary objective of the present invention is the provision of an improved method of forming a trenchless flow line using directional drilling.
Another objective of the present invention is the provision of a method of pilot stem control during directional drilling of a flow line.
A further objective of the present invention is the provision of an improved method of back reaming a directionally drilled bore for a flow line.
Still another objective of the present invention is the provision of a method of supporting the boring tool during drilling so as to overcome gravity drop of the tool in vertical sight relief holes.
Another objective of the present invention is the provision of a method of forming a flow line using a minimum of steps.
A further objective of the present invention is the provision of a method of forming a flow line using directional drilling having close tolerance between the bore and the pipe.
Still another objective of the present invention is the provision of a method of forming a flow line using directional drilling wherein the slurry in the bored hole is pushed ahead of the pipe and is forced into vertical sight relief holes as the pipe is pulled through the bored hole.
Yet another objective of the present invention is the provision of an improved method of forming a trenchless flow line which is accurate and cost effective.
These and other objectives will become apparent from the following description of the invention.